What is typically added around lightning holes to strengthen the area?

Flanges are typically added around lightning holes to enhance the strength and structural integrity of the surrounding area. Lightning holes are precisions cut-outs in aircraft structural components that reduce weight but can potentially weaken the material around them. By incorporating flanges, you create a stronger structural edge, which distributes loads more evenly and helps to prevent crack propagation. This reinforcement is crucial for maintaining the overall strength of the structure, especially in areas that may be subject to fluctuating aerodynamic forces or stresses during flight.

In this context, braces, patches, and rings are not typically utilized for this specific purpose. Braces are more commonly used to support the overall structure by providing additional support in specific loading conditions. Patches can be utilized for repairs, but they would not specifically relate to the structural strengthening around lightning holes during fabrication or design. Rings may have applications in load distribution or fastening but do not serve the strengthening purpose that flanges provide around lightning holes.